We continue the cleaning of strongly_regular_db.pyx.

This ticket is built on top of #34311, #34312 and #34313 to avoid conflicts.

Depends on #34311
Depends on #34312
Depends on #34313

Component: graph theory

Author: David Coudert

Branch/Commit: 08e2a27

Reviewer: Matthias Koeppe

Issue created by migration from https://trac.sagemath.org/ticket/34314